This photo of Saturn was taken by NASA’s Hubble Space Telescope on October 22, 2023, when the ringed planet was approximately 850 million miles from Earth. Hubble’s extremely sensitive view reveals a phenomenon called ring bars.

Saturn’s spokes are transitional elements that rotate with the rings. Ghostly appearances only last for two or three orbits around Saturn. During active periods, freshly made knitting needles constantly complete the pattern.

In 1981, NASA’s Voyager 2 took the first photograph of the ring-shaped spokes. NASA’s Cassini orbiter also saw spokes during its 13-year mission that ended in 2017.

Hubble continues its annual observations of Saturn as the bars appear and disappear. This cycle was captured by the Hubble Outer Planets Atmospheric Heritage (OPAL) program, which began about a decade ago to annually monitor weather changes on the four outer gas giant planets.

Sharp Hubble images show that the frequency of fingerprints depends on the season; It first appears in the OPAL data from 2021, but only appears on the morning (left) side of the rings. Long-term observations show that both the number and contrast of spokes vary depending on Saturn’s season. Saturn, like Earth, is tilted on its axis and has seasons lasting about seven years.

“As we move toward Saturn’s equinox, we expect the stripe strings to be at their peak and more frequent and darker stripes to appear over the next few years,” said OPAL principal scientist Amy Simon of NASA’s Goddard Space Flight Center in Greenbelt. Maryland

This year, these temporary structures are appearing on both sides of the planet simultaneously as the giant orbits the earth. Although they appear small compared to Saturn, their length and width can exceed the diameter of the Earth!

“The main theory is that the spokes are related to Saturn’s strong magnetic field through some interaction with the Sun’s magnetic field that forms the spokes,” Simon said. As Saturn approaches the equinox, the planet and its rings become less inclined relative to the Sun. In this configuration, the solar wind could exert a stronger influence on Saturn’s enormous magnetic field, enhancing the formation of bars.

Planetary scientists believe that the electrostatic forces created by this interaction lift dust or ice from the ring, creating spokes, but for decades no theory has been able to accurately predict the spokes. Hubble’s continued observations may eventually help solve the mystery.